The Django Web Application Framework 2

The Django Web Application
Framework

zhixiong.hong
2009.3.26

Outline
 Overview
 Architecture
 Modules
 Example
 Links

Outline
 Overview
 Architecture
 Example
 Modules
 Links

Web Application Framework
 Define
“A software framework that is designed to support the development of
dynamic website, Web applications and Web services”(from wikipedia)
 The ideal framework
 Clean URLs
 Loosely coupled components
 Designer-friendly templates
 As little code as possible
 Really fast development

Web Application Framework(cont..)
 Ruby
Ruby on Rails (famous, beauty)
 Python
Django, TurboGears, Pylons, Zope, Quixote,web2py(simple)
 PHP
CakePHP, CodeIgniter, PRADO, ThinkPHP,QeePHP (poor performance)
 Others
Apache, J2EE, .NET...(complex)

Web Application Framework(cont..)
Comparsion

What a Django
 “Django is a high-level Python web framework that
encourages rapid development and clean, pragmatic
design.”
 Primary Focus
 Dynamic and database driven website
 Content based websites

Django History
 Named after famous Guitarist “Django Reinhardt”
 Developed by Adrian Holovaty & Jacob Kaplan-moss
 Open sourced in 2005
 1.0 Version released Sep.3 2008, now 1.1 Beta

Why Use Django
 Lets you divide code modules into logical groups to make it flexible
to change
MVC design pattern (MVT)
 Provides auto generated web admin to ease the website
administration
 Provides pre-packaged API for common user tasks
 Provides you template system to define HTML template for your
web pages to avoid code duplication
DRY Principle
 Allows you to define what URL be for a given Function
Loosely Coupled Principle
 Allows you to separate business logic from the HTML
Separation of concerns
 Everything is in python (schema/settings)

Django as an MVC Design Pattern
MVT Architecture:
 Models
Describes your data structure/database schema
 Views
Controls what a user sees
 Templates
How a user sees it
 Controller
The Django Framework
URL dispatcher

Architecture Diagram

Brower

Template URL dispatcher

View

Model

DataBase

Model

Brower


View

Model

DataBase

Model Overview
SQL Free
ORM
Relations
API

Model

class Category(models.Model):
name = models.CharField(max_length=200)
slug = models.SlugField(unique=True)

class Entry(models.Model):
title = models.CharField(max_length=200)
slug = models.SlugField(unique=True)
body = models.TextField()
data = models.DateTimeField(default=datetime.now)
categories = models.ManyToManyField(Category)

python manage.py syncdb

Model API
>>> category = Category(slug='django', name='Django')
>>> category.save()
>>> print category.name
u'Django'

>>> categories = Category.objects.all()
>>> categories = Category.objects.filter(slug='django')
>>> categories
[<Category: Category object>]

>>> entry = Entry(slug='welcome', title='Welcome', body='')
>>> entry.save()
>>> entry.categories.add( category[0] )
>>> print entry.categories.all()
[<Category: Category object>]

View

Brower


View

Model

DataBase

View

def entry_list(request):
entries = Ebtry.objects.all()[:5]
return render_to_response('list.html', {'entries': entries})

def entry_details(request, slug):
entry = get_object_or_404(Entry, slug = slug)
return render_to_response('details.html', {'entry': entry})

Template

Brower


View

Model

DataBase

Template Syntax
 {{ variables }}, {% tags %}, filters (list.html)

<html>
<head>
<title>My Blog</title>
</head>
<body>
{% for entry in entries %}
<h1>{{ entry.title|upper }}</h1>
{{ entry.body }}<br/>
Published {{ entry.data|date:quot;d F Yquot; }},
<a href=”{{ entry.get_absolute_url }}”>link</a>.
{% endfor %}
</body>
</html>

Tag and Filter
 Build in Filters and Tags
 Custom tag and filter libraries
Put logic in tags
{% load comments %}
<h1>{{ entry.title|upper }}</h1>
{{ entry.body }}<br/>
Published {{ entry.data|date:quot;d F Yquot; }},
<a href=”{{ entry.get_absolute_url }}”>link</a>.
<h3>评论: </h3>
{% get_comment_list for entry as comment_list %}
{% for comment in comment_list %}
{{ comment.content }}
{% endfor %}

Template Inheritance
base.html index.html
<html>
<head>
<title>
{% extend “base.html” %}
{% block title %}
{% block title %}
{% endblock %}
Main page
</title>
{% endblock %}
</head>
{% block body %}
<body>
Content
{% block body %}
{% endblock %}
{% endblock %}
</body>
</html>

URL Dispatcher

Brower

Template URL Dispatcher

View

Model

DataBase

URL Dispatcher

urlpatterns = patterns('',
#http://jianghu.leyubox.com/articles/
((r'ârticles/$', ‘article.views.index'), )

#http://jianghu.leyubox.com/articles/2003/
(r'ârticles/(?P<year>d{4})/$', ‘article.views.year_archive'),

# http://jianghu.leyubox.com/articles/2003/ 12/
(r'ârticles/(?P<year>d{4})/(?P<month>d{2})/$',
'article.views.month_archive'),

# http://jianghu.leyubox.com/articles/2003/ 12/3
(r'ârticles/(?P<year>d{4})/(?P<month>d{2})/(?P<day>d+)/$',
'article..views.article_detail'), )

Modules
 Form
 Adminstration interface
 Custom Middleware
 Caching
 Signals
 Comments system
 More...

Modules:Form

class ContactForm(forms.Form):
subject = forms.CharField(max_length=100)
message = forms.CharField(widget=forms.Textarea)
sender = forms.EmailField()
cc_myself = forms.BooleanField(required=False)

<form action=quot;/contact/quot; method=quot;POSTquot;>
{{ form.as_table}}
<input type=quot;submitquot; value=quot;Submitquot; />
</form>

Modules:Adminstration interface

Modules: Custom Middleware
chain of processes

request response
Common Session Authentication Profile
Middleware Middleware Middleware Middleware

Modules: Caching

Memcached Database Filesystem Local-memory Dummy

BaseCache

template caching
Per-View Caching
Per-Site Caching

Modules:More...
 Sessions
 Authentication system
 Internationalization and localization
 Syndication feeds(RSS/Atom)
 E-mail(sending)
 Pagination
 Signals

Example
 django_admin startproject leyubbs
 modify setting.py
 set database options
 append admin app: django.contrib.admin
 python manager.py syncdb
 python manager.py runserver
 modify urls.py, append /admin path

Example(cont...)
 python manager.py startapp article
 add a model
 python manager.py syncdb
 explore admin page
 inset a record in adminstration interface
 add a veiw function
 add a url

Links: Resource
 http://www.djangoproject.com/
For more information (Documentation,Download and News)

 http://www.djangobook.com/
A Good book to learn Django

 http://www.djangopluggables.com
A lot of Django Pluggables available online Explore at

 http://www.pinaxproject.com/
Community Development

The Django Web Application Framework 2

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